422       PREVENTING  THE  BUMPING  OF  BOILING  LIQUIDS. 
lodinized  starch  paper  (1  KT,  10  starch  and  200  water) 
moistened  with  the  above  solution  of  copper  and  suspended  in  a 
10-litre  vessel  containing  one  or  two  drops  of  the  above  hydro- 
cyanic acid,  turns  red ;  the  color  disappears  again  after  some 
time,  in  consequence  of  the  formation  of  iodide  of  cyanogen  and 
hydriodic  acid  ;  this  reaction  indicates  IHCy  in  2,000,000  soln- 
t\ou.—lMd.  67-69. 
ON  SOME  MEANS  FOR  PREVENTING  THE  BUMPING  OF 
BOILING  LIQUIDS. 
By  Hugo  Muller,  F.  R.  S. 
The  annoyance  which  arises  from  the  bumping  of  certain  liq- 
uids when  submitted  to  distillation  or  boiling  has  often  attracted 
the  attention  of  chemists,  and  various  means  have  been  proposed 
for  its  prevention. 
The  value  of  pieces  of  platinum,  charcoal,  burnt  clay,  and 
other  porous  bodies  for  this  purpose  is  well  known,  and  under 
certain  circumstances  are  efficient  enough  ;  yet  there  occur  very 
frequently  cases  in  the  laboratory  when  these  means  are  unavail- 
able. 
About  two  years  ago  Pietro  Pellogio  {Fresenius  Zeitschr.,  vi, 
Jahrg.)  proposed  a  very  simple  contrivance,  which  was  stated  to 
act  very  satisfactorily  indeed.  It  consisted  of  a  moderately  wide 
glass  tube,  passing  through  the  cork  of  the  tubular  of  the  retort, 
and  nearly  reaching  the  bottom  of  it,  the  upper  end  being  bent 
at  right  angles  and  drawn  out  into  a  capillary  tube. 
Having  occasion  to  try  the  efficiency  of  this  arrangement,  I 
came  to  the  conclusion  that  it  was  quite  ineffective,  and  shortly 
after  G.  Hager  {Pharynae.  Central-halhy  Bd.  9)  confirmed  the 
negative  results  I  obtained. 
Quite  recently  E.  Winkelhofer  {Ber.  d,  Chem.  CfesellscL  Ber- 
lin, p.  194, 1869)  proposed  for  the  same  purpose  the  application 
of  an  electric  current,  which,  through  the  incipient  decomposition 
of  the  liquid  and  consequent  evolution  of  gas,  causes  the  ebulli- 
tion to  become  quite  regular  and  steady.  Dufour,  for  another, 
with  another  object  in  view,  had  made  use  of  the  same  means. 
The  application  of  the  electric  current  unfortunately  presup- 
